Pink flowers represent innocence and youth. Giving pink flowers to a lover can represent romantic love rather than the passion of the red flowers.
Yellow flowers have several meanings. It's for example the colour of gold and so is associated with purity and clarity.
The bold energy and warmth of orange flowers symbolises adventure, warmth and enthusiasm.
To quote Shakespeare: 'A rose by any other name would smell as sweet'. We could fill pages about the rose, perhaps the most famous flower in the world, a universal symbol of love and highly revered by gardeners.